A new analysis released by the National Bureau of Economic Research (abstract available here) tracks the changes among the five leading economics journals from 1970 to 2012. Among the trends over that time span:

Annual submissions to the top-5 journals nearly doubled.

The total number of articles published declined from 400 per year to 300 per year.

One journal, American Economic Review, now accounts for 40 percent of publications among these five publications, up from 25 percent.